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Cocrystals of 6‐chlorouracil and 6‐chloro‐3‐methyluracil: exploring their hydrogen‐bond‐based synthon motifs with several triazine and pyrimidine derivatives
Author(s) -
Gerhardt Valeska,
Egert Ernst
Publication year - 2015
Publication title -
acta crystallographica section b
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.604
H-Index - 33
ISSN - 2052-5206
DOI - 10.1107/s2052520615003790
Subject(s) - hydrogen bond , synthon , chemistry , cocrystal , crystal engineering , molecule , triazine , melamine , solvent , halogen , crystal structure , pyrimidine , intermolecular force , polymer chemistry , crystallography , medicinal chemistry , stereochemistry , organic chemistry , alkyl
In order to obtain complexes held together by hydrogen as well as halogen bonds, 6‐chlorouracil [6‐chloropyrimidin‐2,4(1 H ,3 H )‐dione; 6CU] and its 3‐methyl derivative [6‐chloro‐3‐methylpyrimidin‐2,4(1 H ,3 H )‐dione; M6CU] were cocrystallized with 2,4,6‐triaminopyrimidine and the three triazine derivatives 2,4,6‐triamino‐1,3,5‐triazine (melamine), 2,4‐diamino‐6‐methyl‐1,3,5‐triazine and 2‐chloro‐4,6‐diamino‐1,3,5‐triazine, which all offer complementary hydrogen‐bonding sites. Three of these compounds form cocrystals with 6CU; however, melamine yielded only a new pseudopolymorph with 6CU, but formed a cocrystal with M6CU. All six cocrystals contain solvent molecules ( N , N ‐dimethylformamide, N , N ‐dimethylacetamide or N ‐methylpyrrolidin‐2‐one), whose intermolecular interactions contribute significantly to the stabilization of the crystal packing. Each of these structures comprises chains, which are primarily formed by strong hydrogen bonds with a basic framework built by R 2 2 (8) hydrogen bonds of either pure N—H...N or mixed patterns. Solvent molecules are aligned to the border of these chains via N—H...O hydrogen bonds. Two of the reported crystal structures containing 6CU show additional Cl...O halogen bonds, which connect the chains to two‐dimensional layers, while one weak and one strong Cl...Cl interaction are observed in the two structures in which molecules of M6CU are present.